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I'm not a PHP programmer, but I am familiar with the XOOPS core and how templates and themes are used.
Essentially, to get this level of functionality would, at minimum, require some template and theme hacks, if not some Core hacks.
I cannot say how long or how hard it would be too do as I'm a PHP n00b; however, one of the following companies may be able to give you a reasonable quote.
http://www.cusix.dk/
http://inboxinternational.com/
http://www.instant-zero.com/
I'd love to see something like this made into a module. Considering the power of the XOOPS SMARTY system, I would think it would be possible.
The lights are on... nobody's home